The Yaesu ATAS-120A is an active tuning mobile antenna system. When used with the FT-450D it will cover 40 through 6 meters. It provides this great coverage utilizing automatic motorized tuning. It is the successor to the ATAS-100. It utilizes control signals from the transceiver via the coaxial cable. Then the ATAS-120's internal motor adjusts the radiator length for the optimum SWR. This antenna does not come with coax cable or vehicle mount.

It can also be used for fixed base VHF operation with the addition of the optional ATBK-100 VHF/UHF counterpoise kit. In the case of the FT-450, this would be applicable to 6 meter operation only.